Question: Which of the following numbers is a factor of 56? ${2,3,5,9,11}$
By definition, a factor of a number will divide evenly into that number. We can start by dividing $56$ by each of our answer choices. $56 \div 2 = 28$ $56 \div 3 = 18\text{ R }2$ $56 \div 5 = 11\text{ R }1$ $56 \div 9 = 6\text{ R }2$ $56 \div 11 = 5\text{ R }1$ The only answer choice that divides into $56$ with no remainder is $2$ $ 28$ $2$ $56$ We can check our answer by looking at the prime factorization of both numbers. Notice that the prime factors of $2$ are contained within the prime factors of $56$ $56 = 2\times2\times2\times7 2 = 2$ Therefore the only factor of $56$ out of our choices is $2$. We can say that $56$ is divisible by $2$.